Staying independent with age may hinge on staying fit.

According to a new study, individuals with arthritis who avoid exercise double their risk of being unable to perform such everyday tasks as dressing, bathing and cooking in their "golden years."

Seniors who didn't exercise regularly were 90 percent more likely to have a functional decline in their ability to perform these basic activities of daily living, researchers report in the April issue of Arthritis and Rheumatism.

"The important message from this study, especially for people with arthritis, is that participating in regular physical activity will help maintain the ability to live independently as you age," said the study's lead author, Dorothy Dunlop, a research associate professor at the Institute for Healthcare Research at Northwestern University's Feinberg School of Medicine in Chicago.

Osteoarthritis affects almost 21 million Americans, according to the Arthritis Foundation. Arthritis is a leading cause of disability, and one in 10 people with arthritis report difficulties completing everyday tasks, according to background information in the study.

The current study tracked the activity of almost 6,000 people over age 65 for two years. All had been diagnosed with arthritis.

The researchers collected data on demographic characteristics, such as age, race, sex and marital status, as well as information on each participant's health status and chronic health conditions. They also asked about behaviors that could affect the participants' health, such as smoking, exercise, alcohol consumption and dieting.

Functional limitations were assessed based on the ability to perform basic activities of daily living (ADL), which includes walking across a room, dressing, bathing, eating and using the toilet. "Higher-level" daily activities include preparing hot meals, shopping for groceries, making telephone calls, taking medications and managing money.

Overall, 19.7 percent reported trouble performing either ADL tasks or higher-level daily activities. Almost 13 percent of the group weren't able to perform at least one ADL, 5.6 percent couldn't perform at least two basic tasks, and 2.9 percent had trouble completing at least three basic tasks of daily living.

During the two-year study period, 14 percent of the study participants experienced a measurable reduction in their abilities to complete everyday tasks.

The biggest risk factor for having a significant functional decline was a lack of regular and vigorous exercise. Almost two-thirds of the group said they didn't exercise on a regular basis. According to Dunlop, this lack of regular exercise almost doubles the risk of functional decline.

If the study volunteers had exercised, the researchers estimated the loss of functional abilities would have been reduced by about one-third.

"The take-home message is that motivating older adults with arthritis who are not currently engaged in physical activity to participate in regular vigorous exercise could substantially reduce the progression of disability," said Dunlop.

"This study gives us a little more reason to continue preaching the exercise gospel to our patients," said Dr. Joseph Guettler, director of sports medicine education and research at Beaumont Hospital in Royal Oak, Mich. "It scientifically quantifies what we already know is important."

Guettler said osteoarthritis can set up a vicious cycle in which the pain leads people to stop exercising, which then leads to worsening of their symptoms, which leads to further disuse.

Exercise programs are a cornerstone of any arthritis treatment plan, Guettler added, because exercise helps maintain the flexibility of the joints and improves the strength of the muscles around the joints.

"Any exercise with a fluid motion -- without the pound -- such as swimming, walking, biking, etc., can be helpful," he said.

Dunlop said that while her study didn't look at the specific amount of exercise someone should get, the Surgeon General's guidelines are a good place to start. That means you should be participating in about 30 minutes of moderate physical activity most days of the week, she said.

For people with arthritis just starting on an exercise program, Dunlop suggested contacting the local chapter of the Arthritis Foundation. Experts there can recommend local exercise programs designed specifically for people with arthritis, she said.